Non-myeloablative hematopoietic cell transplantation (HCT) followed by delayed donor leukocyte infusion[unreadable] (DLI) is a promising immunotherapeutic approach to treat hematologic malignancies including leukemias and[unreadable] lymphomas. Major limitations of this approach, however, include the risks of graft failure, graft-versus-host[unreadable] disease, (GVHD) and infection. MGH MHC-inbred miniature swine provide a pre-clinical model for studies of[unreadable] transplantation biology with responses to HCT resembling those of humans. Preliminary data suggest that a[unreadable] novel, minimally myelosuppressive preparative regimen leads to stable multilineage chimerism following highdose[unreadable] haploidentical HCT, without causing GVHD. In this proposal we aim to 1) determine the immunological[unreadable] mechanisms involved in controlling hbst-versus-graft (HVG) and GVH responses that allow engraftment[unreadable] without GVHD across MHC barriers in this model. These studies will be performed in close collaboration with[unreadable] Projects 1 and 2 to extend the mechanistic studies in rodent models. We will then 2) optimize the swine[unreadable] model to facilitate translation of this protocol to the clinic and analyze the importance of specific genetic[unreadable] disparities (haploidentical class I and II, class I only, class II only) on engraftment, GVHD and the effects of[unreadable] subsequent DLI. In collaboration with Project 4, we will test novel strategies to improve stem cell harvests[unreadable] following cytokine mobilization through parathyroid hormone (PTH) stimulation. Increased numbers of stem[unreadable] cells in the leukapheresis product following PTH stimulation and cytokine mobilization may enable stable[unreadable] engraftment using lower doses of cells more easily attainable in the clinic. It is hoped that results of these[unreadable] studies will permit the development of tailored approaches to the use of DLI in chimeric patients depending[unreadable] on their HLA disparities from the donor. In addition, we plan to 3) further develop the swine model to allow[unreadable] direct assessment of graft-versus-tumor effects of HCT and DLI. For this purpose, we will establish tumor cell[unreadable] lines derived from inbred miniature swine and adapt these tumor lines for in vivo growth in pigs. With the[unreadable] recent availability of histocompatible miniature swine, and tumor lines derived from these highly inbred[unreadable] animals, we have the unique opportunity to develop transplantable tumors in a preclinical large animal model.[unreadable] These studies could provide a foundation for future immunotherapeutic approaches for the treatment of[unreadable] hematological malignancies that may be translated toward treatment of human disease.[unreadable]